Neural Tube Defects and Prenatal Diagnosis

ACRANIA-ANENSEPHALIA COMPLEX,

It is a fetal malformation in which the skull base and facial bone structures develop but the skull bone structures do not develop, the brain tissue is sometimes not seen at all, and sometimes it is seen as a mass with a malformed structure. Anencephaly can be thought of as the final stage/result of peer, in which the brain tissue deprived of the protection of the skull bone structure deteriorates, deforms and gradually shrinks.

SPINA BIFIDA,

It can be defined as the insufficiency and/or failure in the development and closure of the bone structures forming the posterior part of the canal through which the spinal cord passes in one or more of the vertebrae that make up the spine. It is of two types.

  • Occult (closed/latent) type spina bifida: It constitutes approximately 15% of spinal closure anomalies. It rarely causes neurological problems. In this anomaly, there is no soft tissue opening and skin tissue defect accompanying bone closure insufficiency.

It may be associated with; vertebral defects (80-90%), lumbosacral skin lesions (80%), eg local hair growth, dimple, sinus, increased pigmentation and nevus, subcutaneous mass.

  • Open type spina bifida: It constitutes approximately 85% of spinal closure anomalies. In addition to the bone defect, there is also a skin and soft tissue defect, and the neural elements in the spinal canal and their membranes protrude through the canal through the opening to form a cystic mass. It causes neurological problems at a rate higher than 90%.

  • 1. Simple meningocele: The appearance of a simple cystic sac filled with cerebrospinal fluid without neural elements.

  • 2. Myelocele: At the level of bone and soft tissue defect, neural tissue elements are exposed without skin protection.

  • 3. Myelomeningocele: There are neural tissue elements and membranes in the cystic sac filled with cerebrospinal fluid that extends out of the skin at the level of the bone and soft tissue defect.

  • 4. Myeloschisis: There is a superficial location of the neural elements that are not covered with membranes.

In the fetal detailed ultrasound examination (fetal malformation scan or anomaly scan) performed between 18-24 weeks in the prenatal period, open type spina bifida creates detectable findings and intrauterine diagnosis is possible. The probability of detecting signs of occult spina bifida is low.

In the presence of open type spina bifida, the findings that can be detected in the fetus in ultrasound examination are as follows; bone defect and deformity in the lumbar region is seen. At this level meningocele or meningocele sac may or may not be seen. In the presence of this problem in the lumbar region, due to the deterioration in the circulation of the cerebrospinal fluid and the negative pressure in the skull, the skull shape resembles a lemon. lemon signcerebrospinal fluid-filled cisterna magna behind the cerebellum, which is seen when the cerebellum takes a banana-like shape due to the thinning or disappearance of the cavity. banana signenlargement of cerebrospinal fluid spaces in the brain called ventricles ventriculomegaly-hydrocephalusdetectable findings.

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